CREATE PACKAGE emp_actions AS
/* Declare externally visible types, cursor, exception. */
TYPE EmpRecTyp IS RECORD (emp_id INTEGER, salary REAL);
TYPE DeptRecTyp IS RECORD (dept_id INTEGER, location VARCHAR2);
CURSOR desc_salary RETURN EmpRecTyp;
salary_missing EXCEPTION;
/* Declare externally callable subprograms. */
FUNCTION hire_employee (
ename VARCHAR2,
job VARCHAR2,
mgr NUMBER,
sal NUMBER,
comm NUMBER,
deptno NUMBER) RETURN INTEGER;
PROCEDURE fire_employee (emp_id INTEGER);
PROCEDURE raise_salary (emp_id INTEGER, increase NUMBER);
FUNCTION nth_highest_salary (n INTEGER) RETURN EmpRecTyp;
END emp_actions;
CREATE PACKAGE BODY emp_actions AS
number_hired INTEGER; -- visible only in this package
/* Fully define cursor specified in package. */
CURSOR desc_salary RETURN EmpRecTyp IS
SELECT empno, sal FROM emp ORDER BY sal DESC;
/* Fully define subprograms specified in package. */
FUNCTION hire_employee (
ename VARCHAR2,
job VARCHAR2,
mgr NUMBER,
sal NUMBER,
comm NUMBER,
deptno NUMBER) RETURN INTEGER IS
new_empno INTEGER;
BEGIN
SELECT empno_seq.NEXTVAL INTO new_empno FROM dual;
INSERT INTO emp VALUES (new_empno, ename, job,
mgr, SYSDATE, sal, comm, deptno);
number_hired := number_hired + 1;
RETURN new_empno;
END hire_employee;
PROCEDURE fire_employee (emp_id INTEGER) IS
BEGIN
DELETE FROM emp WHERE empno = emp_id;
END fire_employee;
PROCEDURE raise_salary (emp_id INTEGER, increase NUMBER) IS
current_salary NUMBER;
BEGIN
SELECT sal INTO current_salary FROM emp
WHERE empno = emp_id;
IF current_salary IS NULL THEN
RAISE salary_missing;
ELSE
UPDATE emp SET sal = sal + increase
WHERE empno = emp_id;
END IF;
END raise_salary;
FUNCTION nth_highest_salary (n INTEGER) RETURN EmpRecTyp IS
emp_rec EmpRecTyp;
BEGIN
OPEN desc_salary;
FOR i IN 1..n LOOP
FETCH desc_salary INTO emp_rec;
END LOOP;
CLOSE desc_salary;
RETURN emp_rec;
END nth_highest_salary;
/* Define local function, available only in package. */
FUNCTION rank (emp_id INTEGER, job_title VARCHAR2)
RETURN INTEGER IS
/* Return rank (highest = 1) of employee in a given
job classification based on performance rating. */
head_count INTEGER;
score NUMBER;
BEGIN
SELECT COUNT(*) INTO head_count FROM emp
WHERE job = job_title;
SELECT rating INTO score FROM reviews
WHERE empno = emp_id;
score := score / 100; -- maximum score is 100
RETURN (head_count + 1) - ROUND(head_count * score);
END rank;
BEGIN -- initialization part starts here
INSERT INTO emp_audit VALUES (SYSDATE, USER, 'EMP_ACTIONS');
number_hired := 0;
END emp_actions;Remember, the initialization part of a package is run just once, the first time you reference the package. So, in the last example, only one row is inserted into the database table emp_audit. Likewise, the variable number_hired is initialized only once.
Every time the procedure hire_employee is called, the variable number_hired is updated. However, the count kept by number_hired is session specific. That is, the count reflects the number of new employees processed by one user, not the number processed by all users.
In the next example, you package some typical bank transactions. Assume that debit and credit transactions are entered after business hours via automatic teller machines, then applied to accounts the next morning.
CREATE PACKAGE bank_transactions AS
/* Declare externally visible constant. */
minimum_balance CONSTANT NUMBER := 100.00;
/* Declare externally callable procedures. */
PROCEDURE apply_transactions;
PROCEDURE enter_transaction (
acct NUMBER,
kind CHAR,
amount NUMBER);
END bank_transactions;
CREATE PACKAGE BODY bank_transactions AS
/* Declare global variable to hold transaction status. */
new_status VARCHAR2(70) := 'Unknown';
/* Use forward declarations because apply_transactions
calls credit_account and debit_account, which are not
yet declared when the calls are made. */
PROCEDURE credit_account (acct NUMBER, credit REAL);
PROCEDURE debit_account (acct NUMBER, debit REAL);
/* Fully define procedures specified in package. */
PROCEDURE apply_transactions IS
/* Apply pending transactions in transactions table
to accounts table. Use cursor to fetch rows. */
CURSOR trans_cursor IS
SELECT acct_id, kind, amount FROM transactions
WHERE status = 'Pending'
ORDER BY time_tag
FOR UPDATE OF status; -- to lock rows
BEGIN
FOR trans IN trans_cursor LOOP
IF trans.kind = 'D' THEN
debit_account(trans.acct_id, trans.amount);
ELSIF trans.kind = 'C' THEN
credit_account(trans.acct_id, trans.amount);
ELSE
new_status := 'Rejected';
END IF;
UPDATE transactions SET status = new_status
WHERE CURRENT OF trans_cursor;
END LOOP;
END apply_transactions;
PROCEDURE enter_transaction (
/* Add a transaction to transactions table. */
acct NUMBER,
kind CHAR,
amount NUMBER) IS
BEGIN
INSERT INTO transactions
VALUES (acct, kind, amount, 'Pending', SYSDATE);
END enter_transaction;
/* Define local procedures, available only in package. */
PROCEDURE do_journal_entry (
/* Record transaction in journal. */
acct NUMBER,
kind CHAR,
new_bal NUMBER) IS
BEGIN
INSERT INTO journal
VALUES (acct, kind, new_bal, sysdate);
IF kind = 'D' THEN
new_status := 'Debit applied';
ELSE
new_status := 'Credit applied';
END IF;
END do_journal_entry;
PROCEDURE credit_account (acct NUMBER, credit REAL) IS
/* Credit account unless account number is bad. */
old_balance NUMBER;
new_balance NUMBER;
BEGIN
SELECT balance INTO old_balance FROM accounts
WHERE acct_id = acct
FOR UPDATE OF balance; -- to lock the row
new_balance := old_balance + credit;
UPDATE accounts SET balance = new_balance
WHERE acct_id = acct;
do_journal_entry(acct, 'C', new_balance);
EXCEPTION
WHEN NO_DATA_FOUND THEN
new_status := 'Bad account number';
WHEN OTHERS THEN
new_status := SUBSTR(SQLERRM,1,70);
END credit_account;
PROCEDURE debit_account (acct NUMBER, debit REAL) IS
/* Debit account unless account number is bad or
account has insufficient funds. */
old_balance NUMBER;
new_balance NUMBER;
insufficient_funds EXCEPTION;
BEGIN
SELECT balance INTO old_balance FROM accounts
WHERE acct_id = acct
FOR UPDATE OF balance; -- to lock the row
new_balance := old_balance - debit;
IF new_balance >= minimum_balance THEN
UPDATE accounts SET balance = new_balance
WHERE acct_id = acct;
do_journal_entry(acct, 'D', new_balance);
ELSE
RAISE insufficient_funds;
END IF;
EXCEPTION
WHEN NO_DATA_FOUND THEN
new_status := 'Bad account number';
WHEN insufficient_funds THEN
new_status := 'Insufficient funds';
WHEN OTHERS THEN
new_status := SUBSTR(SQLERRM,1,70);
END debit_account;
END bank_transactions;In this package, the initialization part is not used.